"...especially if they are using Octane or the like as a denaturing agent. "

Isn't that a main ingredient in gasoline!

Wow, that is bloody TERRIBLE

Edited by hikin_jim on 12/22/2011 11:11:31 MST.

"I'm also still very curious to do a side by side test of Green denatured vs. Everclear. I still believe the denaturants are contributing to the soot."

Before you start changing anything with stove designs, etc, try the fuel comparison. I would guess you have the answer right there.

"Isn't that a main ingredient in gasoline!"
Supposed to be. Several different isotopes, longer chained, shorter chained organics involved, too.

> "Isn't that a main ingredient in gasoline!"

Short answer: gasoline contains over 200 compounds including several percent of isomers of octane. The exact ratio varies with the source crude oil and has varied over the years as refining processes have been varied to improve yield, fuel specifications, and smog requirements.

Longer answer (this is part of my day job): "Octane Rating" measures the knock resistence or the ability to be compressed without igniting the gasoline vapors prematurely. 100% iso-octane would have a rating of 100. 95% iso-octane and 5% heptane would have a rating of 95. Lower compression engines can use lower rated fuels. Higher compression engines MUST use higher rated fuels.

But "91 octane" gasoline isn't 91% iso-octane. It's maybe 1-2% iso-octane and a few percent of other octanes. It's got hundreds of different hydrocarbons in it, most because they were in the orginal crude oil, others are added to improve octane rating, higher volatility compounds are included for cold-starting capacity (and are varied summer to winter), and oxygenated compounds (MTBE, ethanol, etc) are added to reduce tailpipe emissions. Plus there are traces amounts of detergent to keep the fuel lines clean and dye (amber for leaded, pink for unleaded, purple for untaxed, etc).

David,

Thank you for that. Interesting stuff.

So if there's only 1 - 2% octane in the gasoline, how do they come up with the Octane rating?

HJ
Adventures in Stoving

Before you start changing anything with stove designs, etc, try the fuel comparison. I would guess you have the answer right there

Edited by hikin_jim on 12/22/2011 13:22:56 MST.

> "So if there's only 1 - 2% octane in the gasoline, how do they come up with the Octane rating?"

Only as a way to measure pre-detonation of the fuel-air mixture. Iso-octane is a very centralized molecule and therefore needs higher temps to ignite. Heptane is very linear and therefore ignites at lower temps.



We could measure human heights on a scale of Herve Villechaize = 0 and Michael Jordan = 100. It doesn't mean that at a rating of 85 you are composed of 85% Michael Jordan. Only that your height falls at that point on the line. And, like octane rating, you could have heights above 100. Aviation gasoline in WWII got up to "150 octane" for use in very high-performance, high-compression engines. But don't me started on how it was actually chemical engineers who won the war.

Editted to add: Herve Villechaize = 1970's reference to the midget actor famous for: "Da plane, boss! Da plane!" as that Grumman G-44 Widgeon amphibious airplane was on short final for Fantasy Island.

Edited by DavidinKenai on 12/22/2011 13:52:08 MST.

Ha ha, Don't even think of asking what is in White Gas. You really don't want to know, nor do the distillers.

Mostly, and in it's easiest understood form, a fractionating tower is a big distilling tower tapped at various temperature levels for various components. A very crude type example...

This means that any substance that forms some eutectic at some temperure will evaporate together/condense together. (Again, a simplistic example and ignoring vapour pressures of the variuos products in the crude.)

Soo, like distilling alcohol mixed with water, it is not 100% alcohol.

Light prodicts go one place to be combined with catylists and heat into larger chained products. Longer chaned products go into other chemical tanks with cataylists to break them down.Both go back into the "gasoline" you burn. Usually the mixes are not octane, unfortunatly. Anyway, depending the exact nature of the crude, the products from distilation and recombination varries.

Additives get added to make up the difference in how the "gasoline" will burn compared with pure octane (a standard.) This is the octane rating. Fuel is different in most batches. You should not notice much difference at the pump, though there are regional and climate differences.

Rule of thumb says use the lowest octane rating available for your car that does NOT lead to spark rattle (predetonation.) But, there are still people out there that use 105 rated gasoline in a family car because they think it gives them more power.

That's nuts. My wood stove leaves less crud than that on the bottom of my pots. I've got hundreds of alcohol stove burns on my Ti pot and it's still perfectly clean.

BM

Ultra,

What type of fuel are you using?

HJ
Adventures in Stoving

Are you sure you weren't testing a wood burning stove with that pot in the picture? ;-)

I go back and forth between ordinary SLX denatured and HEET, whatever I have on hand at the moment.

BM

"I go back and forth between ordinary SLX denatured and HEET, whatever I have on hand at the moment."

The only thing that I like about HEET is the plastic container that it is in. I store S-L-X in mine.

--B.G.--

Mushers up here buy HEET by the case and use it on the trail. They use a metal baking dish, a handful of fiberglass insulation and put a large pot over it to melt snow to broth the dogs. They don't care about efficiency or weight very much because they can have food (4-legged and 2-legged), fuel, batteries, etc, dropped at each village along the way, so they resupply every 150 miles or so (every 1-2 days).

It's all about reliability, simplicity and minimal labor. The dogs rest about half the time. The musher, though, is lucky to sleep 2-3 hours a night for 10 to 15 days.

Ultra Magnus wrote: > I go back and forth between ordinary SLX denatured and HEET, whatever I have on hand at the moment.

David Thomas wrote: > Mushers up here buy HEET by the case and use it on the trail. They use a metal baking dish, a handful of fiberglass insulation and put a large pot over it to melt snow to broth the dogs. They don't care about efficiency or weight very much ...

David Thomas wrote: > ... don't me started on how it was actually chemical engineers who won the war.

HJ, make sure that you add in a pinch of tetraethyl borane.

That was the secret sauce for the JP-7 fuel used by the SR-71 Blackbird.

--B.G.--

>"Say, David, just what is it that you do? ;)"

I design the clean-ups of contaminated soil and groundwater. A ton of service stations throughout California when I was younger than any of us are now. As a senior engineer now, I mostly work on former Air Force Bases, railyards, etc, and other facilities with 2 to 7 million gallons of fuel floating on the groundwater.

In my mind, the idea billing hour is one spent on a conference call, with the cell phone on mute, calling out, "Hey Bear, I don't want to surprise you, bear!" as I hike up the hill on some Alaskan trail and occasionally chiming in on the discussion.

Anyway, back to WWII: The Germans, who were arguable better chemists, got all occupied trying to make liquid fuels from coal and tasked how to kill 6 million Jews. While American ChemE's sat around in their un-bombed offices, with a continent worth of natural resources, and added various steps to the refining process to make very high-octane aviation gasoline. As a result, the P-51 and other planes could have very high-compression, high-effiency engines, and MUCH longer range than pistion-engine planes on the German side. It was what enabled the bombing campaign against Germany because the long-range bombers could then have fighter escorts for the whole run.

At least, that's what the ChemE profs at UC Berkeley told us.